Long Range with CC2640R2F

with Espen Wium & Fredrik Kervel

Hello, my name's Espen Wium, and I'm a systems engineer working on Texas Instruments Bluetooth Low Energy solutions. Today we're outside on the hills surrounding Oslo. And we're going to try the range of the new long-range modes that are being released together with the Bluetooth 5 specification. We have some colleagues of ours poised on an icy lake about 1 kilometers away. They have a simple BLE peripheral, and we will establish a Bluetooth Low Energy connection and see how far they can skate out on the icy lake before we lose that connection.
Hi. My name is Fredrik. I'm an applications engineer with Texas Instruments supporting Bluetooth Low Energy projects. I'm here on Lake [INAUDIBLE] today with the peripheral end of our Bluetooth Low Energy long range Bluetooth 5 link. My colleague Espen is up in the hills there. And I will now take the peripheral and see how far out on the lake I can go while still maintaining a connection. And for that, I brought my skates.
I have now skated a bit out on the lake. Espen is at the top of the hill behind me. The green LED on the board is flashing. You may not be able to see that on this film. But that means that we still have a reliable BLE connection. The distance from Espen to me is at this point about 1 and 1/2 kilometers.
So we have just shown you that with the CC2640R2F, we can get up to 1.5 kilometers of range running Bluetooth 5 coded PHYs. And that's pretty impressive for Bluetooth. So how does this work? Well, there's several ways you can improve your link budgets. One obvious is, of course, to increase the output power in your system. But that will also increase your current consumption. So what Bluetooth sync chose to do was to improve the sensitivity of your receiver instead. And the way they did that was through coding.
So what is coding? Consider regular Bluetooth Low Energy. The data rate is 1 megabit per second. And the over the air symbol rate is 1 mega symbol per second. So that means that for each data bit that you put into the transmitter, you get one physically modulated symbol over the air. With coding, that is different. So you basically use more symbols to represent each data bit. For low energy coded PHYs, there's two stages. So we can either use two symbols per data bit, and this will give us a data rate of 500 kilobits per second. Or we can use eight symbols to represent each data bit. And this will give us a data throughput of 125 kilobits per second.
So how does this work? Well, consider a data bit stream. And let's take one random bit in that bit stream. So we ran forward error correction on the data bits. So in this case, let's take a one going through formal error correction will yield two bits instead. And for the s equal 2, or two symbols per data bit, we use these two directly to represent this single data bit. Now for the eight symbols per data bit, or as Bluetooth sync calls it, s equals 8 [INAUDIBLE], each of these are again expanded by 1 to 4. So a 1 is always represented as 1100, and a 0 is always represented as a 0011. So now we have one data bit being converted to eight symbols. The basic idea here is that this will make it easier for your receiver to interpret your data stream over noise. And that improves sensitivity.
For the CC2640R2F, the sensitivity when running eight-symbol coding is minus 103 dBm. Comparing that to the already best in class sensitivity for 1 megabit per second BLE at minus 97 dBm means that you get a 6 dB improvement in link budget. A very important factor here is that the receiver current consumption is the same as before. And for the CC2640, that is 6 milliamps. So in other words, without increasing the current consumption in your system, you get a 6 dB improvement in your link budget.
As I mentioned earlier, another way to increase the link budget is to increase the TX output power. Many BLE applications transmit at 0 dBm to optimize the power consumption. At 0 dBm, CC2640 consumes 6 milliamps. For this demonstration, we chose a TX power of 5 dBm, which increases the peak current consumption from 6 to 9 milliamps. This is a moderate increase, and will in most cases still allow the system to use the same power supply architecture and energy source. For example, like coin cell battery.
To conclude, we have shown you that by using the new Bluetooth 5 coded PHY, we can achieve a BLE range of more than 1.5 kilometers while still maintaining a peak current consumption below 10 milliamps. Thank you for watching. Please visit our Bluetooth Low Energy web page for more information on how to get started with the CC2640R2F.

Details

Date:
January 20, 2017

The SimpleLink Bluetooth® low energy CC2640R2F wireless MCU supports the new Bluetooth 5 long range modes, also known as coded PHYs.

Three key questions you will be able to answer after viewing this video:

Q 1. How long of a transmission range can be achieved with Bluetooth 5 long range mode?

We are showing 1.6km RF transmission range in this video using the 125kbps coded PHY available as part of the Bluetooth 5 specification. The hardware used is CC2640R2F wireless MCU LaunchPad™ development kit with +5dBm output power. Actual range for your product will depend on antenna performance and the environment where the range test takes place. The best method to ensure adequate range in your application is to try it out using our CC2640R2F LaunchPad kit.

Q 2. What is the difference between Bluetooth 5 long range mode and regular Bluetooth low energy RF transmission?

Bluetooth 5 long range mode (called “Coded PHYs” in the Bluetooth 5 specification) is a coded physical layer with 125kbps data rate, which is 8 times less than the standard 1Mbps Bluetooth low energy RF format. On CC2640R2F, the reduced data rate provides 6dB better sensitivity on the receive side which results in longer RF transmission range.

Q 3. When should I use Bluetooth 5 long range mode?

Long range mode is useful in applications requiring whole-house coverage or longer outdoor RF range than typical Bluetooth applications. Building automation is an application which could benefit from long range mode, where the RF signal often has to pass through walls etc.